1. Field of the Invention
This invention relates generally to a magnetic card reading apparatus for use as a teaching aid, and more particularly to a pressure supply structure in the apparatus which is operated by initially placing the card in position so that it can move the card in a forward direction under a constant pressure and at a uniform speed. The apparatus further may include a card return device which is operated by depressing an appropriate button for moving the card back to its initial position or any selected position.
2. Description of the Prior Art In a conventional apparatus of the type disclosed herein, the magnetic information card is usually read by moving either the card or the magnetic read head or transducer relative to the other, and the movement of the card or head must be at a constant speed. When the head is moved relative to the card which remains stationary, However, problems are involved from both electrical and mechanical standpoints if there is a need for moving the heat at a uniform speed or without any variation in speed within its range of movement. Theoretically, it appears to be less problematical in this respect to move the card relative to the head. Although the above problems may thus be obviated, a different problem must be considered. That is, if it is necessary that the card at regular or uniform speeds along the card path, the card is very likely to slip out of the path. For this reason, the apparatus must be designed and manufactured so as to prevent such slipping of the card and thus to permit the card to travel at a uniform speed. For this purpose, a combination of a pinch roller and a capstan roller may be provided for holding the card under appropriate pressures and thus moving it by the cooperative action of the two rollers on opposite sides of the card. As it is extremely difficult or almost impossible always to place the two rollers in an opposed spaced relation opposite so that a passage can be defined therebetween which has a predetermined gap smaller than the thickness of the card, it is possible that as an alternative to bring the pinch roller into contact with the capstan roller with an appropriate pressure. In this alternative form, the pinch roller is made of resilient material such as rubber, and the capstan roller is made of metal. It is not desirable, however, that the two rollers always be kept in contact as described above since the rubber pinch roller can be damaged or worn by the frictional resistance between the rollers or can be subjected to deformation due to the pressure of the metallic capstan roller. In the light which are present in the above problems of the alternative form of the device, it is desirable that the two rollers be capable of being so moved away from each other when the apparatus is not in use, whereas during operation of the apparatus they are moved closer to each other for holding the card therebetween under pressure. The above operation of the two rollers can be accomplished by means of an associated handle such as a lever handle operated for opening and closing the lid of the apparatus independently or regardless of the presence of a card on the card path, but this may possibly make the operation of the apparatus difficult since a complex the operation is involved as can readily be understood from the above.
Upon completion of the reading of the card the trailing end of which has traveled past the transducer head, or at any desired position of the card which is traveling forward, it is also desirable that the card can be selectively moved back to its initial position or to any selected position without the necessity of removing the card from the apparatus and then placing it in a starting position again so that the desired information on the card can be obtained over again. It is very clear, however, that time consuming operations are necessary for removing the card and replacing it in the starting position, and it is also necessary to ensure that the card is placed in the proper starting position each time the card is read. There is known a conventional apparatus of the type which also includes a card return device which is selectively operable for selectively moving the card back to its initial position or to any selected position. In the conventional return device, a card is moved back by means of the power driven roller which includes a gear engageable with the gear of a driving roller. Thus, depression of the control button causes the gear of the driven roller to engage the gear of the driving roller and then to bring the driven roller into contact with the card, thus moving it backward. As readily understood from the the above, the two gears which are selectively engageable with each other, become worn by long-time repeated use thereof. This may result in lack of accuracy with which the card is returned at a constant speed and under a uniform pressure.